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  1. #1
    Join Date
    Jul 2006
    Looking at all the love there that's sleeping

    "Moth effect" - blinking or steady tail lights?

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    Hi all.
    My DH pointed out an email that a guy posted on the LBS listserv. I've pasted it below (it's fairly long), so it may contain their typos.
    Basically - it's about why you should NOT use your taillight on "blinking mode" but rather - steady. They refer to it as the "moth effect" that it causes drivers - especially drunk ones - to fixate on it and potentially steer right towards it and hit you. I seem to recall that somewhere (across the pond...England? Somewhere "over there") it is illegal to use blinking lights on a bike. Perhaps this is the reason why?
    Anywho...I wanted to get your thoughts on this. I routinely set my light to blink, as I generally figured it was more visible that way. Maybe it's visible to my detriment?

    Hey, came across this information about tail lights on bikes, thought it might be useful, see below (the I is not me), Frank

    In early November I met a young lady here in the OBX who was cycling from Maine to Florida . She related this story to me. When she was pedaling through Virginia a state trooper stopped her while riding at night. She was using a good headlight and a blinking red tail light. The trooper said to her that a blinking red tail light attracts drunk drivers (he explained a drunkard doesn't seem to understand the significance of the blinking red light and drives towards the cyclist out of curiosity with sometimes tragic consequences). The trooper strongly recommended that she and all cyclists use a solid red beam on the tail light as opposed to the blinking mode.

    This morning I sent an email to a company that, according to the New York Times, makes the best bike tail light in the world ( Andrew Martinez sent the NYT article to me about the company and light and I was following up with the company). In an email to them I mentioned the trooper's comments above. In their response, the company stated:

    QUOTE: YES-- this is called the Moth Effect and has been written about and documented by the International Chief of Police (IACP) Association. UNQUOTE

    I looked for additional information on the web re "moth effect" and found it not only impacts cyclists vis--vis drunk drivers, but also impacts any vehicle with blinking lights and sober drivers.

    Here's a quote from one source:

    QUOTE What Causes The Moth-Effect?

    The moth effect seems to have two enabling conditions. The first is minimal optic flow information, as when a driver is on a dark road at night or perhaps traveling in bad weather. The second is an intense attentional fixation on a roadside target. The lack of optic flow likely removes the normal source of heading information, forcing the driver to rely on a sense of egocentric direction relative to a landmark the fixated object. When people look in the direction of travel, the egocentric straight-ahead direction and eye direction are the same. When people fixate away from the direction of travel, then they must then use knowledge of eye position to calculate maintain a proper sense of egocentric direction. If the calculation is correct, then the person has maintained directional constancy. Studies (e. g., Hill, 1972; (Morgan, 1978) show that people are unable to maintain their sense of egocentric direction when fixating eccentrically. Instead, the sense of straight-ahead moves in the direction of fixation. In other words, the driver looking right while attempting to travel down the road straight will steer to the right of roadway in an attempt to steer straight.

    The intense attentional focus can play several roles. Attention is a zero-sum game, so the more attention focused on one task, the less available to others. Concentrating attention on a target might reduce attention available to maintaining directional constancy. It might also prevent the driver from noticing cues for steering correction. The perceptual narrowing might prevent the driver from monitoring road delineations in peripheral vision. The driver would not be aware they he last lost lane positioning. Similarly, the driver may fail to notice to tactile cues that occur when a driver leaves the paved roadway. Research (Summala, 1998) shows that steering becomes generally erratic when drivers fixate eccentrically.

    Lastly, drivers who start with less attentional resource should suffer a greater chance of suffering the moth-effect. Drivers who are fatigued, bored, affected by drugs or alcohol, or older should be more prone to steer off the road. However, it is not these conditions that directly cause the result. It is the way they affect distribution of attention. UNQUOTE

  2. #2
    Join Date
    May 2006
    This is really interesting. I think the comments they make about attentional processes are valid. I can understand how you would become fixated (even if you werent drunk) on the light to ensure you knew exactly where the cyclist was.

    I've always used a blinking light because I've been worried about the "sensory adaptation" effect of a single, constant beam. Kind of like when you wear a watch, it's always there so you are not consciously aware of it. But if you put it on the other wrist you'd notice it for a while until your senses just adapted to it and "tuned it out".

    Now i'm wondering if I should have two lights - one that is a constant red light so that drivers will easily know where i am on the road, and another that blinks so that it keeps stimulating drivers attention and they dont just zone out and forget i'm there.

    Interesting stuff.
    To know even one life has breathed easier because you have lived This is to have succeeded - Emerson

  3. #3
    Join Date
    Jul 2006
    Riding my Luna & Rivendell in the Hudson Valley, NY
    Unfortunately you get about 3 or 4 times the battery life when you use your blinkies in fashing mode than when you have them on steady. Read about battery life on each blinkie's info sheet and you'll see. That would tend to make people always put them on in flashing mode.
    Our bikes...OurBikes...and my mountain dulcimer blog
    Ruby's Website and My blog

  4. #4
    Join Date
    Oct 2002
    San Francisco Bay Area
    I don't think flashing lights are allowed on brevets, except to indicate an emergency.

    I keep mine on steady. I am a vehicle, vehicles only have flashing lights to indicate turns or emergencies.

    Discipline is remembering what you want.


  5. #5
    Join Date
    Apr 2006
    In Arkansas they just passed a law for motorcycles that says for daytime riding, they can have their headlights blinking instead of steady.

    The only reason that's relevant is because of what you said about being a vehicle. Exception proves the rule.


  6. #6
    Join Date
    Jun 2005
    ... oh, and vehicles use flashing lights if they are moving slowly. A bicycle is (usually) a slow-moving vehicle, relatively speaking.
    So... who's more likely to be sharing the road with me? A drunkard or a regular dude who might not notice one more solid red thing? 'Cause the basic principal could be that anything that attracts attention attracts the car of the drunk... but with that logic, I should try to be invisible... that's the strategy of an awful lot of riders around here, and I *don't* read about 'em being knocked down as often as it would seem, but I'm not sure I want to go that way.
    (I tend to have both solid and flashing, myself.)
    Last edited by Geonz; 12-16-2006 at 09:09 PM.

  7. #7
    Join Date
    Sep 2005
    Trondheim, Norway
    I'm not riding this time of year. I walk as much as I can, but also drive some. And as a driver I am veeeery grateful for bikers/walkers with flashing lights. And also reflective strips. It's scary when suddenly a dark figure appears just 10 feet in front of you, only visible as a shadow in the lights of an oncoming car. Even a teensy steady bike light (maybe running out of power) helps some, but a flashing one helps more. And folks with a reflector vest, bright yellow with big reflective stripes on it, can be seen from as far away as my own lights, or those of a vehicle ahead of me, can reach. I do NOT veer over towards them. In the dark, they're competing for attention with other spots of light -- oncoming vehicles, street lighting (which in some cases can distract as much as it lights up), xmas decorations. What's unlit tends to disappear into the void. And remember that, even with your lights on, you're invisible to oncoming traffic when you come out from behind some other vehicle. So I slow down so as to have better stop time when the inevitable surprises appear in the dark, but boy do they scare me sometimes. Case in point a few days ago: Black-clad biker, with no lights or reflectors, and no helmet, swerves out from behind a parked vehicle on a largely single-lane road (due to parking on one side) and head-on into my lane! He was darned lucky I was going slow and managed to stop!
    Half-marathon over. Sabbatical year over. It's back to "sacking shirt and oat cakes" as they say here.

  8. #8
    Join Date
    Oct 2006
    Reporting from Moonshine Mountain
    Very interesting thread. I had not heard it called the "moth effect" but it makes sense. I have always used a blinking light but maybe now I should try a steady one? I don't know. I rarely ride in the dark but use mine during the day.

    Something else to consider is that there are more and more drivers out there who are driving sleepy. I have read stories of cars pulled off the highway because of a flat tire or something, and a zoned-out driver slams into the rear of the car because he didn't realize it was stopped.

    We are taking our lives in our hands when we get out there with 2000 lb. missles whizzing by us, so I think it really doesn't matter what we do - just have a light on & bright clothing to make ourselves as visible as possible. Any light, blinking or steady, is better than no light.
    "When I'm on my bike I forget about things like age. I just have fun." Kathy Sessler

    2006 Independent Fabrication Custom Ti Crown Jewel (Road, though she has been known to go just about anywhere)/Specialized Jett

  9. #9
    Join Date
    Apr 2007
    I have read stories of cars pulled off the highway because of a flat tire or something, and a zoned-out driver slams into the rear of the car because he didn't realize it was stopped.
    It happened to me but I was the crashee, not the crasher.

    Totaled my brand new Yugo. Yes, Yugo.

  10. #10
    Join Date
    May 2013
    this is certainly an old thread

    A steady light allows a driver to perceive depth more easily for a better positional reference of a bike rider.
    I saw revolights on a bike a few months ago and was impressed. It's a kickstarter company. Not good enough battery life for what I need though.

    Last edited by rebeccaC; 07-07-2013 at 05:50 PM.

  11. #11
    Join Date
    Sep 2007
    Uncanny Valley
    If someone's target-fixated on me, I'm not sure how much difference their depth perception makes. They correct when (and if) they notice what they're doing. They don't make a decision that they've gotten close enough and now it's time to stop steering towards me. You learn a lot from being a pedestrian that cyclists with their backs to overtaking traffic never see.

    It's pretty obvious to me that a blinking light is more noticeable than a solid one. Pay attention some time when you're behind someone in low visibility conditions, motorized or not. Or what about those radar signs that strobe at you when you're doing more than 10 over the limit? They get your attention pretty good, eh.

    I think there are good arguments for motorcyclists to be as invisible as possible, because with a motor and a throttle and good attention and skills, we can get out of most trouble that we let ourselves get into. Not so much for bicyclists. The same as with my hi-viz clothing, I choose to be as visible as possible, even though I'm well aware of the risks of target fixation. At least 20% of motorists will do the right thing when they see me. That's about the same percentage as target fixate, but it's a much higher percentage than those who target fixate AND don't correct in plenty of time. As I say so often, I choose to be visible for two reasons: first, as a courtesy to motorists who ARE paying attention, and second, for the benefit of my loved ones if something does happen, since almost universally when a non-motorized road user is struck, the authorities and/or juries make it their fault, and wearing the wrong clothes and gear is the #1 way we are blamed.
    Last edited by OakLeaf; 07-08-2013 at 03:46 AM.
    Speed comes from what you put behind you. - Judi Ketteler

  12. #12
    Join Date
    Jan 2006
    I use a solid light in nighttime conditions but a blinking light in dusky/rainy/poor visibility conditions. Though for most true nighttime riding (going home from work every day in fall and winter) I use a helmet light of which the rear light can only blink, and put the bike's taillight on solid. I've had drivers tell me I was very visible and they wished all cyclist were as visible.
    Oil is good, grease is better.

    2007 Peter Mooney w/S&S couplers/Terry Butterfly
    1993 Bridgestone MB-3/Avocet O2 Air 40W
    1980 Columbus Frame with 1970 Campy parts
    1954 Raleigh 3-speed/Brooks B72

  13. #13
    Join Date
    Feb 2005
    Concord, MA
    I have a large solid, car type rear light on my Guru, which is standard equipment and required in most European countries. However, when I am riding early in the AM, in the real dark (fall/spring) I also add a blinkie, attached to my rear bag or my back. I keep my front light on solid until it is clearly dawn and the sky is all light. Then I might keep it on flashing for awhile after that. In the fall, actually starting in late August, I will use my front light on flashing mode if I am riding in the late afternoon, as I live in a very shaded area and the shadows are horrendous. Sunset might not be for 2 more hours, but I have been driving home from work and have passed many, many cyclists who are almost invisible.
    2015 Trek Silque SSL
    Specialized Oura

    2011 Guru Praemio
    Specialized Oura

  14. #14
    Join Date
    Dec 2005
    WA State
    My personal observation is that cyclists who, like myself, ride mainly in the city after dark are much more noticeable with a flashing light (front or rear) than with a solid one. In the areas that I frequent there's lots of other things that are lit and or/reflect and small, steady bike lights just don't compete very well, so I nearly always use mine on blink (well one front one on blink - I have a steady so I can see too). I can't say I really worry about moth effect under these conditions either - that happens when motorists are on straight, fast stretches of road and can zone out. On city streets you can't drive like that as you are always stopping/starting/turning.
    "Sharing the road means getting along, not getting ahead" - 1994 Washington State Driver's Guide

    visit my flickr stream http://flic.kr/ps/MMu5N

  15. #15
    Join Date
    Sep 2006
    Washington, DC
    My tail light, a Light & Motion Vis 180, has both in one of its settings (the default one, upon turning it on): the top is steady and the bottom pulses. I am really pleased with that light.



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